OceanStor Cache Statistics Test

A cache is a key module that improves performance and user experience. Cache configurations on the performance of read/write functions are of immense importance. To read data, the cache prefetches it to increase the hit ratio and reduce the number of read I/Os delivered to disks, thereby minimizing the latency and providing a higher performance. When reading data from a LUN, the storage system prefetches data from disks to the cache based on non-prefetch, intelligent prefetch, constant prefetch, or variable prefetch policies. If a prefetch policy is set inappropriately, excessive or insufficient prefetch may occur. To understand how the caches are utilized and to promptly capture abnormalities in cache usage, administrators have to continuously monitor the requests processed in the cache. This is what exactly the OceanStor Cache Statistics test does!

This test continuously tracks the cache on the target storage system and reports the percentage of cache utilized to process read/write requests and the hit ratio of the cache. This way, administrators can figure out the ineffective request processing patterns of the cache, which may contribute to a slowdown in operations.

Target of the test: Huawei OceanStor

Agent deploying the test: A remote agent

Outputs of the test: One set of results for each cache in the Huawei OceanStor that is being monitored.

Descriptor: Cache

Configurable parameters for the test
Parameter	Description
Test period	How often should the test be executed.
Host	The IP address of the target host to be monitored.
SNMPPort	The port at which the monitored target exposes its SNMP MIB; the default value is 161.
Data Over TCP	By default, in an IT environment, all data transmission occurs over UDP. Some environments however, may be specifically configured to offload a fraction of the data traffic – for instance, certain types of data traffic or traffic pertaining to specific components – to other protocols like TCP, so as to prevent UDP overloads. In such environments, you can instruct the eG agent to conduct the SNMP data traffic related to the monitored target over TCP (and not UDP). For this, set this flag to Yes. By default, this flag is set to No.
Timeout	Specify the duration (in seconds) within which the SNMP query executed by this test should time out in this text box. The default is 10 seconds.
SNMPVersion	By default, the eG agent supports SNMP version 1. Accordingly, the default selection in the SNMPversion list is v1. However, if a different SNMP framework is in use in your environment, say SNMP v2 or v3, then select the corresponding option from this list.
SNMPCommunity	The SNMP community name that the test uses to communicate with the switch. This parameter is specific to SNMP v1 and v2 only. Therefore, if the SNMPVersion chosen is v3, then this parameter will not appear.
Context	This parameter appears only when v3 is selected as the SNMPVERSION. An SNMP context is a collection of management information accessible by an SNMP entity. An item of management information may exist in more than one context and an SNMP entity potentially has access to many contexts. A context is identified by the SNMPEngineID value of the entity hosting the management information (also called a contextEngineID) and a context name that identifies the specific context (also called a contextName). If the USERNAME provided is associated with a context name, then the eG agent will be able to poll the MIB and collect metrics only if it is configured with the context name as well. In such cases therefore, specify the context name of the USERNAME in the CONTEXT text box. By default, this parameter is set to none.
Username	This parameter appears only when v3 is selected as the SNMPVERSION. SNMP version 3 (SNMPv3) is an extensible SNMP Framework which supplements the SNMPv2 Framework, by additionally supporting message security, access control, and remote SNMP configuration capabilities. To extract performance statistics from the MIB using the highly secure SNMP v3 protocol, the eG agent has to be configured with the required access privileges - in other words, the eG agent should connect to the MIB using the credentials of a user with access permissions to be MIB. Therefore, specify the name of such a user against this parameter.
AuthPass	Specify the password that corresponds to the above-mentioned Username. This parameter once again appears only if the SNMPversion selected is v3.
Confirm Password	Confirm the AuthPass by retyping it here.
AuthType	This parameter too appears only if v3 is selected as the SNMPversion. From the AuthType list box, choose the authentication algorithm using which SNMP v3 converts the specified username and password into a 32-bit format to ensure security of SNMP transactions. You can choose between the following options: MD5 - Message Digest Algorithm SHA - Secure Hash Algorithm SHA224 - Secure Hash Algorithm 224 bit SHA256 - Secure Hash Algorithm 256 bit SHA384 - Secure Hash Algorithm 384 bit SHA512 - Secure Hash Algorithm 512 bit
EncryptFlag	This flag appears only when v3 is selected as the SNMPVersion. By default, the eG agent does not encrypt SNMP requests. Accordingly, this flag is set to No by default. To ensure that SNMP requests sent by the eG agent are encrypted, select the Yes option.
EncryptType	If the EncryptFlag is set to Yes, then you will have to mention the encryption type by selecting an option from the EncryptType list. SNMP v3 supports the following encryption types: DES - Data Encryption Standard 3DES - Triple Data Encryption Standard AES - Advanced Encryption Standard AES128 - Advanced Encryption Standard 128 bit AES192 - Advanced Encryption Standard 192 bit AES256 - Advanced Encryption Standard 256 bit
EncryptPassword	Specify the encryption password here.
Confirm Password	Confirm the encryption password by retyping it here.
EngineID	This parameter appears only when v3 is selected as the SNMPVersion. Sometimes, the test may not report metrics when AES192 or AES256 is chosen as the Encryption type. To ensure that the test report metrics consistently, administrators need to set this flag to Yes. By default, this parameter is set to No.

Measurements made by the test
Measurement	Description	Measurement Unit	Interpretation
Read utilization	Indicates the percentage of read operations performed by this cache.	Percent
Write utilization	Indicates the percentage of write operations performed by this cache.	Percent
Cache hit ratio	Indicates the percentage of requests that was serviced by this cache.	Percent	A higher value for this measure is a sign of a healthy cache. A very low value indicates that the cache is unable to serve most of the I/O requests and the data is served directly from the backend storage.